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the purposes I have in view in this work, to consider them particularly. The moderns too, have been much divided on the subject; some holding with Des Cartes, that the mind is furnished with certain innate ideas; others, with Mr. Locke, that all our ideas may be traced from sensation and reflection; and many, (especially among the later metaphysicians in France,) that they may be all traced from sensation

alone.

Of these theories, that of Mr. Locke deserves more particularly our attention; as it has served as the basis of most of the metaphysical systems which have appeared since his time; and as the difference between it and the theory which derives all our ideas from sensation alone, is rather apparent than real

In order to convey a just notion of Mr. Locke's doctrine concerning the origin of our ideas, it is necessary to remark, that he refers to sensation all the ideas, which we are supposed to receive by the external senses, our ideas, for example, of colours, of sounds, of hardness, of extension, of motion, and in short, of all the qualities, and modes of matter; to reflection, the ideas of our own mental operations, which we derive from consciousness; our ideas, for example, of memory, of imagination, of volition, of pleasure, and of pain. These two sources, according to him, furnish us with all our simple ideas, and the only power which the mind possesses over them, is to perform certain operations, in the way of composition, abstraction, generalization, &c. on the materials which it thus collects in the course of its experience.The laudable desire of Mr. Locke, to introduce precision and perspicuity into metaphysical speculations, and his anxiety to guard the mind against error in general, naturally prepossessed him in favour of a doctrine, which, when compared with those of his predecessors, was intelligible and simple, and which, by suggesting a method, apparently easy and palpable, of analyzing our knowledge into its elementary principles, seemed to furnish an antidote against those prejudices which had been favoured by the hypothesis of innate ideas. It is now a considerable time since this fundamental principle of Mr. Locke's system began to lose its authority in England; and the scepticalconclusions, which it had been employed to support by some later writers, furnished its opponents with very plausible arguments against it. The late learned Mr. Harris, in particular, frequently mentions this doctrine of Mr. Locke, and always in terms of high indignation. "Mark," (says he, in one passage,) "the order of things, according to the account of our late "metaphysicians. First, comes that huge body, the sensible world."Then this, and its attributes, beget sensible ideas. Then, out of sensi"ble ideas, by a kind of lopping and pruning, are made ideas intelligi❝ble, whether specific or general. Thus, should they admit that mind ❝was coëval with body; yet till body gave it ideas, and awakened its "dormant powers, it could at best have been nothing more than a sort "of dead capacity; for innate ideas it could not possibly have any." And, in another passage: "For my own part, when I read the detail "about sensation and reflection, and am taught the process at large "how my ideas are all generated, I seem to view the human soul in the "light of a crucible, where truths are produced by a kind of logical " chemistry."

If Dr. Reid's reasonings on the subject of ideas be admitted, all these speculations with respect to their origin fall to the ground, and the question to which they relate, is reduced merely to a question of fact, concerning the occasions on which the mind is first led to form those simple notions, into which our thoughts may be analyzed, and which may be considered as the principles or elements of human knowledge. With respect to many of these notions, this inquiry involves no difficul ty. No one, for example, can be at a loss to ascertain the occasions on which the notions of colours and sounds are first formed by the mind: for these notions are confined to individuals who are possessed of particular senses, and cannot, by any combination of words, be conveyed to those who never enjoyed the use of them. The history of our notions of extension and figure, (which may be suggested to the mind by the exercise either of sight or of touch,) is not altogether so obvious; and accordingly, it has been the subject of various controversies. To trace the origin of these, and of our other simple notions with respect to the qualities of matter, or, in other words to describe the occasions on which, by the laws of our nature, they are suggested to the mind, is one of the leading objects of Dr. Reid's inquiry, in his analysis of our external senses; in which he carefully avoids every hypothesis with respect to the inexplicable phenomena of perception and of thought, and confines himself scrupulously to a literal statement of facts. Similar inquiries to these may be proposed, concerning the occasions on which we form the notions of time, of motion, of number, of causation, and an infinite variety of others. Thus, it has been observed by different authors, that every perception of change suggests to the mind the notion of a cause, without which that change could not have happened. Dr. Reid remarks, that, without the faculty of memory, our perceptive powers could never have led us to form the idea of motion. I shall afterwards shew, in the sequel of this work, that without the same faculty of memory, we never could have formed the notion of time; and that without the faculty of abstraction, we could not have formed the notion of number. Such inquiries, with respect to the origin of our knowledge, are curious and important, and if conducted with judgment, they may lead to the most certain conclusions; as they aim at nothing more than to ascertain facts, which although not obvious to superficial observers, may yet be discovered by patient investigation.

From the remarks which have been just made on our notions of time, of motion, and of number, it is evident that the inquiry concerning the origin of human knowledge cannot possibly be discussed at the commencement of such a work as this; but that it must be resumed in different parts of it, as those faculties of the mind come under our view, with which the formation of our different simple notions is connected. With respect to the general question, Whether all our knowledge may be ultimately traced from our sensations? I shall only observe at present, that the opinion we form concerning it is of much less consequence than is commonly supposed. That the mind cannot, without the grossest absurdity, be considered in the light of a receptacle which is gradually furnished from without, by materials introduced by the channel of the senses, nor in that of a tabula rasa upon which copies or resemblances of things external are imprinted, I have already shewn at sufficient length. Although, therefore, we should acquiesce in the

conclusion, that, without our organs of sense, the mind must have remained destitute of knowledge, this concession could have no tendency whatever to favour the principles of materialism; as it implies nothing more, than that the impressions, made on our senses by external objects, furnish the occasions, on which the mind, by the laws of its constitution, is led to perceive the qualities of the material world, and to exert all the different modifications of thought of which it is capable.

From the very slight view of the subject, however, which has been already given, it is sufficiently evident, that this doctrine, which refers the origin of all our knowledge to the occasions furnished by sense, must be received with many limitations. That those ideas, which Mr. Locke calls ideas of reflection, (or, in other words, the notions which we form of the subjcets of our own consciousness,) are not suggested to the mind immediately by the sensations arising from the use of our organs of perception, is granted on all hands: and, therefore, the amount of the doctrine now mentioned, is nothing more than this; that the first. occasions on which our various intellectual faculties are exercised, are furnished by the impressions made on our organs of sense, and cousequently, that, without these impressions, it would have been impossible for us to arrive at the knowledge of our faculties. Agreeably to this explanation of the doctrine, it may undoubtedly be said with plausibility, (and, I am inclined to believe, with truth,) that the occasions on which all our notions are formed, are furnished either immediately or ultimately by sense; but, if I am not much mistaken, this is not the meaning which is commonly annexed to the doctrine, either by its advocates or their opponents. One thing at least is obvious, that, in this sense, it does not lead to those consequences which have interested one) party of philosophers in its defence, and another in its refutation.

There is another very important consideration which deserves our attention in this argument: that, even on the supposition, that certain impressions on our organs of sense are necessary to awaken the mind to a consciousness of its own existence, and to give rise to the exercise of its various faculties, yet all this might have happened, without our having any knowledge of the qualities, or even of the existence, of the material world. To facilitate the admission of this proposition, let us suppose a being formed in every other respect like man, but possessed of no senses, excepting those of hearing and smelling. I make choice of these two senses, because it is obvious, that by means of them alone we never could have arrived at the knowledge of the primary qualities of matter, or even of the existence of things eternal. All that we could possibly have inferred from our occasional sensations of smell and sound, would have been, that there existed some unknown cause by which they were produced.

Let us suppose then a particular sensation to be excited in the mind of such a being. The moment this happens, he must necessarily acquire the knowledge of two facts at once: that of the existence of the sensation, aud that of his own existence, as á sentient being. After the sensation is at an end, he can remember he felt it; he can conceive that he feels it again. If he has felt a variety of different sensations, he can compare them together in respect of the pleasure or the pain they have afforded him, and will naturally desire the return of the agreeable sensations, and be afraid of the return of those which were painful.-

If the sensations of smell and sound are both excited in his mind at the same time, he can attend to either of them he chooses, and withdraw his attention from the other, or he can withdraw his attention from both and fix it on some sensation he has felt formerly. In this manner, he might be led, merely by sensations existing in his mind, and conveying to him no information concerning matter, to exercise many of his most important faculties; and amidst all these different modifications and operations of his mind, he would feel, with irresistible conviction, that they all belong to one and the same sentient and intelligent being, or, in other words that they are all modifications and operations of him elf. I say nothing at present, of the various simple notions, (or simple ideas as they are commonly called,) which would arise in his mind: for example, the ideas of number, of duration, of cause, and effect, of personal identity; all of which, though perfectly unlike his sensations, could not fail to be suggested by means of them. Such a being, then, might know all that we know of mind at present, and as his language would be appropriated to mind solely, and not borrowed by analogy from material phenomena, he would even possess important advantages over us in conducting the study of pneumatology.

From these observations it sufficiently appears, what is the real amount of the celebrated doctrine, which refers the origin of all our knowledge to our sensations; and that, even granting it to be true, (which for my own part, I am disposed to do, in the sense in which Í have now explained it,) it would by no means follow from it, that our notions of the operations of mind, nor even many of those notions which are commonly suggested to us, in the first instance, by the perception of external objects, are necessarily subsequent to our knowledge of the qualities, or even of the existence of matter.

The remarks which I have offered on this doctrine will not appear superfluous to those who recollect that, although it has, for many years past been a subject of controversy in England, it continues still to be implicitly adopted by the best philosophical writers in France; and that it has been employed by some of them to support the system of materialism, and by others to shew, that the intellectual distinctions between man and brutes arise entirely from the differences in their animal organization and in their powers of external perception.

CHAPTER SECOND.

OF ATTENTION.

WHEN we are deeply engaged in conversation, or occupied with any

speculation that is interesting to the mind, the surrounding objects either do not produce in us the perceptions they are fitted to excite, or these perceptions are instantly forgotten. A clock, for example, may strike in the same room with us, without our being able, next moment, to recollect whether we heard it or not.

In these, and similar cases, I believe, it is commonly taken for granted, that we really do not perceive the external object. From some analogous facts, however, I am inclined to suspect that this opinion is not well founded. A person who falls asleep at church, and is suddenly awaked, is unable to recollect the last words spoken by the preacher ; or even to recollect that he was speaking at all. And yet, that sleep does not suspend entirely the powers of perception, may be inferred from this, that if the preacher were to make a sudden pause in his discourse, every person in the congregation, who was asleep, would instantly awake. In this case, therefore, it appears, that a person may be conscious of a perception, without being able afterwards to recollect it.

Many other instances of the same general fact might be produced.When we read a book, especially in a language which is not perfectly familiar to us,) we must perceive successively every different letter, and must afterwards combine these letters into syllables and words, before we comprehend the meaning of a sentence. This process, however, passes through the mind, without leaving any trace on the memory.

It has been proved by optical writers, that, in perceiving the distances of visible objects from the eye, there is a judgment of the understanding antecedent to the perception. In some cases this judgment is founded on a variety of circumstances combined together; the conformation of the organ necessary for distinct vision; the inclination of the optic axes; the distinctness or indistinctness of the minute parts of the object; the distances of the intervening objects from each other, and from the eye; and, perhaps on other circumstances besides these: and yet, in consequence of our familiarity with such processes from our earliest infancy, the perception seems to be instantaneous; and it requires much reasoning, to convince persons unaccustomed to philosophical speculations, that the fact is otherwise.

Another instance of a still more familiar nature, may be of use for the farther illustration of the same subject. It is well known, that our thoughts do not succeed each other at random, but according to certain laws of association, which modern philosophers have been at much pains to investigate. It frequently, however, happens, particularly when the mind is animated by conversation, that it makes a sudden transition from one subject to another, which, at first view, appears to be very remote from it; and that it requires a considerable degree of reflection, to enable the person himself by whom the transition was made, to ascertain what were the intermediate ideas. A curious instance of such a sudden transition is mentioned by Hobbes in his Leviathan. "In a company," (says he,) "in which the conversation turned "on the civil war, what could be conceived more impertinent, than for a person to ask abruptly, What was the value of a Roman denarius ? "On a little reflection, however, I was easily able to trace the train of "thought which suggested the question; for the original subject of "discourse naturally introduced the history of the King, and of the "treachery of those who surrendered his person to his enemies; this « again introduced the treachery of Judas Iscariot, and the sum of money which he received for his reward -And all this train of ideas," (says Hobbes,)" passed through the mind of the speaker in a twinkling, "in consequence of the velocity of thought." It is by no means impro

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VOL. I.

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